[root@~~/]# rpm -qa | grep mysql
mysql-5.6.28-1.el6.x86_64
[root@~~/]# lsb_release -a
LSB Version:  :core-4.1-amd64:core-4.1-noarch
Distributor ID: CentOS
Description:  CentOS Linux release 7.2.1511 (Core)
Release:    7.2.1511
Codename:    Core
[root@~~/]# uname -r
3.10.0-327.22.2.el7.x86_64

[root@~~/]# vi /etc/my.cnf

[mysqld] 
datadir=/var/lib/mysql 
socket=/var/lib/mysql/mysql.sock 
skip-grant-tables 

[root@~~/]# /etc/init.d/mysqld restart 
Stopping MySQL: [ OK ] 
Starting MySQL: [ OK ]

[root@~~/]# mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.6.28-log Source distribution
Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> use mysql;
mysql> update user set password=password("test") where user='root';
mysql> flush privileges;
mysql> exit; 
Bye

[root@~~/]# vi /etc/my.cnf

[root@~~/]# /etc/init.d/mysqld restart 
Stopping MySQL: [ OK ] 
Starting MySQL: [ OK ]

[root@~~/]# firewall-cmd --permanent --zone=public --add-port=3306/tcp 
success
[root@~~/]# firewall-cmd --reload
success